Values in (1-9) range not in (0-8) range
Implement in_line, in_range boolean methods
Use in_line and in_range methods in Sudoku implementation
Create abstract sudoku.Struct as an interface for Game and Box

Game is a full sudoku game, that contains boxes
Box is a simpler Struct, containing some cells but no complex structs
A Struct object has cells, implements cell key, has a sence of range
but no shape or line functionality here
Unittest sudoku.Struct